In the past electrodes for the electrolysis of brines have been bulk graphite slabs or plates. While such graphite slabs and plates are characterized by having satisfactory electroconductivity, they are subject to attack by the electrode products, to erosion, and to ultimate destruction in service.
To a significant extent, bulk graphite slabs have now been replaced by metallic electrodes. In their most common form, metallic electrodes have a valve metal base with an electroconductive surface. The electroconductive of valve metal substrates that have been used include the valve metals, i.e., titanium, tantalum, tungsten, niobium, zironcium, aluminum, and berylium. Most frequently, titanium substrates have been used.
The valve metal electrodes of the prior art have most commonly had precious metal surfaces. These surfaces have typically been the platinum metals in the metalic state, i.e., platinum, iridium, osmium, palladium, rhodium, and ruthenium. Alternatively, the electroconductive surfaces of these valve metal electrodes of the prior art have included oxides of the platinum group metals as well as other oxygen-containing compounds of the platinum group metals.